1
|
Mi D, Yanatori I, Zheng H, Kong Y, Hirayama T, Toyokuni S. Association of poly( rC)-binding protein-2 with sideroflexin-3 through TOM20 as an iron entry pathway to mitochondria. Free Radic Res 2024; 58:261-275. [PMID: 38599240 DOI: 10.1080/10715762.2024.2340711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Accepted: 03/15/2024] [Indexed: 04/12/2024]
Abstract
Iron is essential for all the lives and mitochondria integrate iron into heme and Fe-S clusters for diverse use as cofactors. Here, we screened mitochondrial proteins in KU812 human chronic myelogenous leukemia cells by glutathione S-transferase pulldown assay with PCBP2 to identify mitochondrial receptors for PCBP2, a major cytosolic Fe(II) chaperone. LC-MS analyses identified TOM20, sideroflexin-3 (SFXN3), SFXN1 and TOM70 in the affinity-score sequence. Stimulated emission depletion microscopy and proteinase-K digestion of mitochondria in HeLa cells revealed that TOM20 is located in the outer membrane of mitochondria whereas SFXN3 is located in the inner membrane. Although direct association was not observed between PCBP2 and SFXN3 with co-immunoprecipitation, proximity ligation assay demonstrated proximal localization of PCBP2 with TOM20 and there was a direct binding between TOM20 and SFXN3. Single knockdown either of PCBP2 and SFXN3 in K562 leukemia cells significantly decreased mitochondrial catalytic Fe(II) and mitochondrial maximal respiration. SFXN3 but not MFRN1 knockout (KO) in mouse embryonic fibroblasts decreased FBXL5 and heme oxygenase-1 (HO-1) but increased transferrin uptake and induced ferritin, indicating that mitochondrial iron entry through SFXN3 is distinct. MFRN1 KO revealed more intense mitochondrial Fe(II) deficiency than SFXN3 KO. Insufficient mitochondrial heme synthesis was evident under iron overload both with SFXN3 and MFRN KO, which was partially reversed by HO-1 inhibitor. Conversely, SFXN3 overexpression caused cytosolic iron deficiency with mitochondrial excess Fe(II), which further sensitized HeLa cells to RSL3-induced ferroptosis. In conclusion, we discovered a novel pathway of iron entry into mitochondria from cytosol through PCBP2-TOM20-SFXN3 axis.
Collapse
Affiliation(s)
- Danyang Mi
- Department of Pathology and Biological Responses, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Izumi Yanatori
- Department of Pathology and Biological Responses, Nagoya University Graduate School of Medicine, Nagoya, Japan
- Department of Molecular and Cellular Physiology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Hao Zheng
- Department of Pathology and Biological Responses, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Yingyi Kong
- Department of Pathology and Biological Responses, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Tasuku Hirayama
- Laboratory of Pharmaceutical and Medicinal Chemistry, Gifu Pharmaceutical University, Gifu, Japan
| | - Shinya Toyokuni
- Department of Pathology and Biological Responses, Nagoya University Graduate School of Medicine, Nagoya, Japan
- Center for Low-temperature Plasma Sciences, Nagoya University, Nagoya, Japan
- Center for Integrated Sciences of Low-temperature Plasma Core Research (iPlasma Core), Tokai National Higher Education and Research System, Nagoya, Japan
| |
Collapse
|
2
|
Yang Y, Wang X, Yuan X, Zhu Q, Chen S, Xia D. Glucose-activatable insulin delivery with charge-conversional polyelectrolyte multilayers for diabetes care. Front Bioeng Biotechnol 2022; 10:996763. [PMID: 36246353 PMCID: PMC9557070 DOI: 10.3389/fbioe.2022.996763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Accepted: 09/06/2022] [Indexed: 11/24/2022] Open
Abstract
One of the most effective treatments for diabetes is to design a glucose-regulated insulin (INS) delivery system that could adjust the INS release time and rate to reduce diabetes-related complications. Here, mixed multiple layer-by-layer (mmLbL)-INS microspheres were developed for glucose-mediated INS release and an enhanced hypoglycemic effect for diabetes care. To achieve ultrafast glucose-activated INS release, glucose oxidase (GOx) was assembled with a positively charged polymer and modified on INS LbL. The mmLbL-INS microspheres were constructed with one, two, and four layers of the polyelectrolyte LbL assembly at a ratio of 1:1:1. Under hyperglycemia, GOx converts a change in the hyperglycemic environment to a pH stimulus, thus providing sufficient hydrogen ion. The accumulated hydrogen ion starts LbL charge shifting, and anionic polymers are converted to cationic polymers through hydrolytic cleavage of amine-functionalized side chains. The results of in vitro INS release suggested that glucose can modulate the mmLbL-INS microspheres in a pulsatile profile. In vivo studies validated that this formulation enhanced the hypoglycemic effect in STZ-induced diabetic rats within 2 h of subcutaneous administration and facilitated stabilization of blood glucose levels for up to 2 days. This glucose-activatable LbL microsphere system could serve as a powerful tool for constructing a precisely controlled release system.
Collapse
Affiliation(s)
- Yanguang Yang
- Department of Radiotherapy, Nantong Tumor Hospital, Tumor Hospital Affiliated to Nantong University, Nantong, China
| | - Xiangqian Wang
- Department of Radiotherapy, Nantong Tumor Hospital, Tumor Hospital Affiliated to Nantong University, Nantong, China
| | - Xiaopeng Yuan
- Department of Radiotherapy, Nantong Tumor Hospital, Tumor Hospital Affiliated to Nantong University, Nantong, China
| | - Qiwei Zhu
- Department of Radiotherapy, Nantong Tumor Hospital, Tumor Hospital Affiliated to Nantong University, Nantong, China
| | - Shusen Chen
- Department of Radiotherapy, Nantong Tumor Hospital, Tumor Hospital Affiliated to Nantong University, Nantong, China
| | - Donglin Xia
- School of Public Health, Nantong University, Nantong, China
- *Correspondence: Donglin Xia,
| |
Collapse
|
3
|
Sedivy P, Dusilova T, Hajek M, Burian M, Krššák M, Dezortova M. In Vitro 31P MR Chemical Shifts of In Vivo-Detectable Metabolites at 3T as a Basis Set for a Pilot Evaluation of Skeletal Muscle and Liver 31P Spectra with LCModel Software. Molecules 2021; 26:molecules26247571. [PMID: 34946652 PMCID: PMC8703310 DOI: 10.3390/molecules26247571] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Revised: 12/06/2021] [Accepted: 12/10/2021] [Indexed: 11/24/2022] Open
Abstract
Most in vivo 31P MR studies are realized on 3T MR systems that provide sufficient signal intensity for prominent phosphorus metabolites. The identification of these metabolites in the in vivo spectra is performed by comparing their chemical shifts with the chemical shifts measured in vitro on high-field NMR spectrometers. To approach in vivo conditions at 3T, a set of phantoms with defined metabolite solutions were measured in a 3T whole-body MR system at 7.0 and 7.5 pH, at 37 °C. A free induction decay (FID) sequence with and without 1H decoupling was used. Chemical shifts were obtained of phosphoenolpyruvate (PEP), phosphatidylcholine (PtdC), phosphocholine (PC), phosphoethanolamine (PE), glycerophosphocholine (GPC), glycerophosphoetanolamine (GPE), uridine diphosphoglucose (UDPG), glucose-6-phosphate (G6P), glucose-1-phosphate (G1P), 2,3-diphosphoglycerate (2,3-DPG), nicotinamide adenine dinucleotide (NADH and NAD+), phosphocreatine (PCr), adenosine triphosphate (ATP), adenosine diphosphate (ADP), and inorganic phosphate (Pi). The measured chemical shifts were used to construct a basis set of 31P MR spectra for the evaluation of 31P in vivo spectra of muscle and the liver using LCModel software (linear combination model). Prior knowledge was successfully employed in the analysis of previously acquired in vivo data.
Collapse
Affiliation(s)
- Petr Sedivy
- MR-Unit, Department of Diagnostic and Interventional Radiology, Institute for Clinical and Experimental Medicine, Videnska 1958/9, 140 21 Prague, Czech Republic; (P.S.); (T.D.); (M.H.); (M.B.)
| | - Tereza Dusilova
- MR-Unit, Department of Diagnostic and Interventional Radiology, Institute for Clinical and Experimental Medicine, Videnska 1958/9, 140 21 Prague, Czech Republic; (P.S.); (T.D.); (M.H.); (M.B.)
| | - Milan Hajek
- MR-Unit, Department of Diagnostic and Interventional Radiology, Institute for Clinical and Experimental Medicine, Videnska 1958/9, 140 21 Prague, Czech Republic; (P.S.); (T.D.); (M.H.); (M.B.)
| | - Martin Burian
- MR-Unit, Department of Diagnostic and Interventional Radiology, Institute for Clinical and Experimental Medicine, Videnska 1958/9, 140 21 Prague, Czech Republic; (P.S.); (T.D.); (M.H.); (M.B.)
| | - Martin Krššák
- Division of Endocrinology and Metabolism, Department of Internal Medicine III, Medical University of Vienna, 1090 Vienna, Austria;
- High-Field MR Center, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, 1090 Vienna, Austria
| | - Monika Dezortova
- MR-Unit, Department of Diagnostic and Interventional Radiology, Institute for Clinical and Experimental Medicine, Videnska 1958/9, 140 21 Prague, Czech Republic; (P.S.); (T.D.); (M.H.); (M.B.)
- Correspondence: ; Tel.: +420-23605-5245
| |
Collapse
|
4
|
Abstract
The uptake of calcium into and extrusion of calcium from the mitochondrial matrix is a fundamental biological process that has critical effects on cellular metabolism, signaling, and survival. Disruption of mitochondrial calcium (mCa2+) cycling is implicated in numerous acquired diseases such as heart failure, stroke, neurodegeneration, diabetes, and cancer, and is genetically linked to several inherited neuromuscular disorders. Understanding the mechanisms responsible for mCa2+ exchange therefore holds great promise for the treatment of these diseases. The past decade has seen the genetic identification of many of the key proteins that mediate mitochondrial calcium uptake and efflux. Here, we present an overview of the phenomenon of mCa2+ transport, and a comprehensive examination of the molecular machinery that mediates calcium flux across the inner mitochondrial membrane: the mitochondrial uniporter complex (consisting of MCU, EMRE, MICU1, MICU2, MICU3, MCUB, and MCUR1), NCLX, LETM1, the mitochondrial ryanodine receptor, and the mitochondrial permeability transition pore. We then consider the physiological implications of mCa2+ flux and evaluate how alterations in mCa2+ homeostasis contribute to human disease. This review concludes by highlighting opportunities and challenges for therapeutic intervention in pathologies characterized by aberrant mCa2+ handling and by summarizing critical unanswered questions regarding the biology of mCa2+ flux.
Collapse
Affiliation(s)
- Joanne F Garbincius
- Center for Translational Medicine, Center for Translational Medicine, Lewis Katz School of Medicine at Temple University, Philadelphia, PA, United States
| | | |
Collapse
|
5
|
Lee JW. Mitochondrial energetics with transmembrane electrostatically localized protons: do we have a thermotrophic feature? Sci Rep 2021; 11:14575. [PMID: 34272427 PMCID: PMC8285424 DOI: 10.1038/s41598-021-93853-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Accepted: 06/07/2021] [Indexed: 01/24/2023] Open
Abstract
Transmembrane electrostatically localized protons (TELP) theory has been recently recognized as an important addition over the classic Mitchell's chemiosmosis; thus, the proton motive force (pmf) is largely contributed from TELP near the membrane. As an extension to this theory, a novel phenomenon of mitochondrial thermotrophic function is now characterized by biophysical analyses of pmf in relation to the TELP concentrations at the liquid-membrane interface. This leads to the conclusion that the oxidative phosphorylation also utilizes environmental heat energy associated with the thermal kinetic energy (kBT) of TELP in mitochondria. The local pmf is now calculated to be in a range from 300 to 340 mV while the classic pmf (which underestimates the total pmf) is in a range from 60 to 210 mV in relation to a range of membrane potentials from 50 to 200 mV. Depending on TELP concentrations in mitochondria, this thermotrophic function raises pmf significantly by a factor of 2.6 to sixfold over the classic pmf. Therefore, mitochondria are capable of effectively utilizing the environmental heat energy with TELP for the synthesis of ATP, i.e., it can lock heat energy into the chemical form of energy for cellular functions.
Collapse
Affiliation(s)
- James Weifu Lee
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, VA, 23529, USA.
| |
Collapse
|
6
|
Moffett JR, Puthillathu N, Vengilote R, Jaworski DM, Namboodiri AM. Acetate Revisited: A Key Biomolecule at the Nexus of Metabolism, Epigenetics and Oncogenesis-Part 1: Acetyl-CoA, Acetogenesis and Acyl-CoA Short-Chain Synthetases. Front Physiol 2020; 11:580167. [PMID: 33281616 PMCID: PMC7689297 DOI: 10.3389/fphys.2020.580167] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2020] [Accepted: 09/23/2020] [Indexed: 12/19/2022] Open
Abstract
Acetate is a major end product of bacterial fermentation of fiber in the gut. Acetate, whether derived from the diet or from fermentation in the colon, has been implicated in a range of health benefits. Acetate is also generated in and released from various tissues including the intestine and liver, and is generated within all cells by deacetylation reactions. To be utilized, all acetate, regardless of the source, must be converted to acetyl coenzyme A (acetyl-CoA), which is carried out by enzymes known as acyl-CoA short-chain synthetases. Acyl-CoA short-chain synthetase-2 (ACSS2) is present in the cytosol and nuclei of many cell types, whereas ACSS1 is mitochondrial, with greatest expression in heart, skeletal muscle, and brown adipose tissue. In addition to acting to redistribute carbon systemically like a ketone body, acetate is becoming recognized as a cellular regulatory molecule with diverse functions beyond the formation of acetyl-CoA for energy derivation and lipogenesis. Acetate acts, in part, as a metabolic sensor linking nutrient balance and cellular stress responses with gene transcription and the regulation of protein function. ACSS2 is an important task-switching component of this sensory system wherein nutrient deprivation, hypoxia and other stressors shift ACSS2 from a lipogenic role in the cytoplasm to a regulatory role in the cell nucleus. Protein acetylation is a critical post-translational modification involved in regulating cell behavior, and alterations in protein acetylation status have been linked to multiple disease states, including cancer. Improving our fundamental understanding of the "acetylome" and how acetate is generated and utilized at the subcellular level in different cell types will provide much needed insight into normal and neoplastic cellular metabolism and the epigenetic regulation of phenotypic expression under different physiological stressors. This article is Part 1 of 2 - for Part 2 see doi: 10.3389/fphys.2020.580171.
Collapse
Affiliation(s)
- John R Moffett
- Department of Anatomy, Physiology and Genetics, and Neuroscience Program, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Narayanan Puthillathu
- Department of Anatomy, Physiology and Genetics, and Neuroscience Program, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Ranjini Vengilote
- Department of Anatomy, Physiology and Genetics, and Neuroscience Program, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Diane M Jaworski
- Department of Neurological Sciences, University of Vermont College of Medicine, Burlington, VT, United States
| | - Aryan M Namboodiri
- Department of Anatomy, Physiology and Genetics, and Neuroscience Program, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| |
Collapse
|
7
|
Kumar R, Chhikara BS, Gulia K, Chhillar M. Cleaning the molecular machinery of cells via proteostasis, proteolysis and endocytosis selectively, effectively, and precisely: intracellular self-defense and cellular perturbations. Mol Omics 2020; 17:11-28. [PMID: 33135707 DOI: 10.1039/d0mo00085j] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Network coordinates of cellular processes (proteostasis, proteolysis, and endocytosis), and molecular chaperones are the key complements in the cell machinery and processes. Specifically, cellular pathways are responsible for the conformational maintenance, cellular concentration, interactions, protein synthesis, disposal of misfolded proteins, localization, folding, and degradation. The failure of cellular processes and pathways disturbs structural proteins and the nucleation of amyloids. These mishaps further initiate amyloid polymorphism, transmissibility, co-aggregation of pathogenic proteins in tissues and cells, prion strains, and mechanisms and pathways for toxicity. Consequently, these conditions favor and lead to the formation of elongated amyloid fibrils consisting of many-stranded β-sheets (N,N-terminus and C,C-terminus), and abnormal fibrous, extracellular, proteinaceous deposits. Finally, these β-sheets deposit, and cells fail to degrade them effectively. The essential torsion angles (φ, ψ, and ω) define the conformation of proteins and their architecture. Cells initiate several transformations and pathways during the regulation of protein homeostasis based on the requirements for the functioning of the cell, which are governed by ATP-dependent proteases. In this process, the kinetics of the molding/folding phenomenon is disturbed, and subsequently, it is dominated by cross-domain misfolding intermediates; however, simultaneously, it is opposed by small stretching forces, which naturally exist in the cell. The ubiquitin/proteasome system deals with damaged proteins, which are not refolded by the chaperone-type machinery. Ubiquitin-protein ligases (E3-Ub) participate in all the cellular activity initiated and governed by molecular chaperones to stabilize the cellular proteome and participate in the degradation phenomenon implemented for damaged proteins. Optical tweezers, a single-resolution based technique, disclose the folding pathway of linear chain proteins, which is how they convert themselves into a three-dimensional architecture. Further, DNA-protein conjugation analysis is performed to obtain folding energies as single-molecule kinetic and thermodynamic data.
Collapse
Affiliation(s)
- Rajiv Kumar
- NIET, National Institute of Medical Science, India.
| | | | | | | |
Collapse
|
8
|
Aghelan Z, Kiani S, Nasiri A, Sadeghi M, Farrokhi A, Khodarahmi R. Factors Influencing Mitochondrial Function as a Key Mediator of Glucose-Induced Insulin Release: Highlighting Nicotinamide Nucleotide Transhydrogenase. INTERNATIONAL JOURNAL OF MOLECULAR AND CELLULAR MEDICINE 2020; 9:107-122. [PMID: 32934948 PMCID: PMC7489113 DOI: 10.22088/ijmcm.bums.9.2.107] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Accepted: 08/04/2020] [Indexed: 12/13/2022]
Abstract
Pancreatic β-cells recognize blood glucose changes and release insulin that is a peptide hormone responsible for stable glycemia. Diabetes, a chronic disorder of insulin insufficiency, leads to disturbed glucose homeostasis and multi-organ problems. Glucose and insulin are key markers in the follow-up and control of this disease. Mitochondrial metabolism of pancreatic beta cells is a crucial part of glucose-stimulated cascade of insulin secretion. Effective factors on β-cells mitochondrial function in production of compounds such as tricarboxylic acid intermediates, glutamate, nicotinamide adenine dinucleotide phosphate, and reactive oxygen species can have great effects on the secretion of insulin under diabetes. This review enhances our knowledge of factors influencing mitochondrial function as a key mediator of glucose-induced insulin release that accordingly will be helpful to further our understanding of the mechanisms implicated in the progressive beta cell failure that results in diabetes.
Collapse
Affiliation(s)
- Zahra Aghelan
- Department of Clinical Biochemistry, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Sara Kiani
- Medical Biology Research Center, Health Technology Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Abolfazl Nasiri
- Department of Clinical Biochemistry, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Masoud Sadeghi
- Medical Biology Research Center, Health Technology Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Alireza Farrokhi
- Medical Biology Research Center, Health Technology Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Reza Khodarahmi
- Medical Biology Research Center, Health Technology Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran
| |
Collapse
|
9
|
Knudsen JG, Hamilton A, Ramracheya R, Tarasov AI, Brereton M, Haythorne E, Chibalina MV, Spégel P, Mulder H, Zhang Q, Ashcroft FM, Adam J, Rorsman P. Dysregulation of Glucagon Secretion by Hyperglycemia-Induced Sodium-Dependent Reduction of ATP Production. Cell Metab 2019; 29:430-442.e4. [PMID: 30415925 PMCID: PMC6370947 DOI: 10.1016/j.cmet.2018.10.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Revised: 07/23/2018] [Accepted: 10/13/2018] [Indexed: 01/21/2023]
Abstract
Diabetes is a bihormonal disorder resulting from combined insulin and glucagon secretion defects. Mice lacking fumarase (Fh1) in their β cells (Fh1βKO mice) develop progressive hyperglycemia and dysregulated glucagon secretion similar to that seen in diabetic patients (too much at high glucose and too little at low glucose). The glucagon secretion defects are corrected by low concentrations of tolbutamide and prevented by the sodium-glucose transport (SGLT) inhibitor phlorizin. These data link hyperglycemia, intracellular Na+ accumulation, and acidification to impaired mitochondrial metabolism, reduced ATP production, and dysregulated glucagon secretion. Protein succination, reflecting reduced activity of fumarase, is observed in α cells from hyperglycemic Fh1βKO and β-V59M gain-of-function KATP channel mice, diabetic Goto-Kakizaki rats, and patients with type 2 diabetes. Succination is also observed in renal tubular cells and cardiomyocytes from hyperglycemic Fh1βKO mice, suggesting that the model can be extended to other SGLT-expressing cells and may explain part of the spectrum of diabetic complications.
Collapse
Affiliation(s)
- Jakob G Knudsen
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LE, UK
| | - Alexander Hamilton
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LE, UK
| | - Reshma Ramracheya
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LE, UK
| | - Andrei I Tarasov
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LE, UK
| | - Melissa Brereton
- Department of Physiology, Anatomy & Genetics, Parks Road, Oxford OX1 3PT, UK
| | - Elizabeth Haythorne
- Department of Physiology, Anatomy & Genetics, Parks Road, Oxford OX1 3PT, UK
| | - Margarita V Chibalina
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LE, UK
| | - Peter Spégel
- Centre for Analysis and Synthesis, Lund University Diabetes Centre, Department of Chemistry, Naturvetarvägen 14, Lund 221 00, Sweden
| | - Hindrik Mulder
- Unit of Molecular Metabolism, Lund University Diabetes Centre, Department of Clinical Research in Malmö, Jan Waldenströms Gata 35, Malmö 205 02, Sweden
| | - Quan Zhang
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LE, UK
| | - Frances M Ashcroft
- Department of Physiology, Anatomy & Genetics, Parks Road, Oxford OX1 3PT, UK
| | - Julie Adam
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LE, UK; Nuffield Department of Clinical Medicine, University of Oxford, NDM Research Building, Oxford OX3 7FZ, UK.
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LE, UK; Metabolic Research, Department of Neuroscience and Physiology, Sahlgrenska Academy, University of Göteborg, Box 433, Göteborg 405 30, Sweden.
| |
Collapse
|
10
|
Chareyron I, Wall C, Thevenet J, Santo-Domingo J, Wiederkehr A. Cellular stress is a prerequisite for glucose-induced mitochondrial matrix alkalinization in pancreatic β-cells. Mol Cell Endocrinol 2019; 481:71-83. [PMID: 30476561 DOI: 10.1016/j.mce.2018.11.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Revised: 11/20/2018] [Accepted: 11/22/2018] [Indexed: 11/24/2022]
Abstract
Changes in mitochondrial and cytosolic pH alter the chemical gradient across the inner mitochondrial membrane. The proton chemical gradient contributes to mitochondrial ATP synthesis as well as the uptake and release of metabolites and ions from the organelle. Here mitochondrial pH and ΔpH were studied for the first time in human pancreatic β-cells. Adenoviruses were used for rat insulin promoter dependent expression of the pH sensor SypHer targeted to either the mitochondrial matrix or the cytosol. The matrix pH in resting human β-cells is low (pH = 7.50 ± SD 0.17) compared to published values in other cell types. Consequently, the ΔpH of β-cells mitochondria is small. Glucose stimulation consistently resulted in acidification of the matrix pH in INS-1E insulinoma cells and β-cells in intact human islets or islet monolayer cultures. We registered acidification with similar kinetics but of slightly smaller amplitude in the cytosol of β-cells, thus glucose stimulation further reduced the ΔpH. Infection of human islets with high levels of adenoviruses caused the mitochondrial pH to increase. The apoptosis inducer and broad-spectrum kinase inhibitor staurosporine had similar effects on pH homeostasis. Although staurosporine alone does not affect the mitochondrial pH, glucose slightly increases the matrix pH of staurosporine treated cells. These two cellular stressors alter the normal mitochondrial pH response to glucose in pancreatic β-cells.
Collapse
Affiliation(s)
- Isabelle Chareyron
- Mitochondrial Function, Nestlé Institute of Health Sciences, 1015, Lausanne, Switzerland
| | - Christopher Wall
- Mitochondrial Function, Nestlé Institute of Health Sciences, 1015, Lausanne, Switzerland
| | - Jonathan Thevenet
- Mitochondrial Function, Nestlé Institute of Health Sciences, 1015, Lausanne, Switzerland
| | - Jaime Santo-Domingo
- Mitochondrial Function, Nestlé Institute of Health Sciences, 1015, Lausanne, Switzerland
| | - Andreas Wiederkehr
- Mitochondrial Function, Nestlé Institute of Health Sciences, 1015, Lausanne, Switzerland.
| |
Collapse
|
11
|
Gerencser AA. Metabolic activation-driven mitochondrial hyperpolarization predicts insulin secretion in human pancreatic beta-cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2018; 1859:817-828. [PMID: 29886047 DOI: 10.1016/j.bbabio.2018.06.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Revised: 05/18/2018] [Accepted: 06/05/2018] [Indexed: 12/31/2022]
Abstract
Mitochondrial metabolism plays a central role in insulin secretion in pancreatic beta-cells. Generation of protonmotive force and ATP synthesis from glucose-originated pyruvate are critical steps in the canonical pathway of glucose-stimulated insulin secretion. Mitochondrial metabolism is intertwined with pathways that are thought to amplify insulin secretion with mechanisms distinct from the canonical pathway, and the relative importance of these two pathways is controversial. Here I show that glucose-induced mitochondrial membrane potential (MMP) hyperpolarization is necessary for, and predicts, the rate of insulin secretion in primary cultured human beta-cells. When glucose concentration is elevated, increased metabolism results in a substantial MMP hyperpolarization, as well as in increased rates of ATP synthesis and turnover marked by faster cell respiration. Using modular kinetic analysis I explored what properties of cellular energy metabolism enable a large glucose-induced change in MMP in human beta-cells. I found that an ATP-dependent pathway activates glucose or substrate oxidation, acting as a positive feedback in energy metabolism. This activation mechanism is essential for concomitant fast respiration and high MMP, and for a high magnitude glucose-induced MMP hyperpolarization and therefore for insulin secretion.
Collapse
Affiliation(s)
- Akos A Gerencser
- Buck Institute for Research on Aging, 8001 Redwood Blvd, Novato, CA 94945, United States; Image Analyst Software, 43 Nova Lane, Novato, CA 94945, United States.
| |
Collapse
|
12
|
Lin B, Fan L, Ge J, Zhang W, Zhang C, Dong C, Shuang S. A naphthalene-based fluorescent probe with a large Stokes shift for mitochondrial pH imaging. Analyst 2018; 143:5054-5060. [DOI: 10.1039/c8an01371c] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
A naphthalene-based fluorescent pH probe with a pKa of 8.8 for imaging mitochondrial pH changes in live cells.
Collapse
Affiliation(s)
- Bo Lin
- College of Chemistry and Chemical Engineering
- Shanxi University
- Taiyuan 030006
- China
| | - Li Fan
- Institute of Environmental Science
- Shanxi University
- Taiyuan 030006
- China
| | - Jinyin Ge
- College of Chemistry and Chemical Engineering
- Shanxi University
- Taiyuan 030006
- China
| | - Wenjia Zhang
- College of Chemistry and Chemical Engineering
- Shanxi University
- Taiyuan 030006
- China
| | - Caihong Zhang
- College of Chemistry and Chemical Engineering
- Shanxi University
- Taiyuan 030006
- China
| | - Chuan Dong
- Institute of Environmental Science
- Shanxi University
- Taiyuan 030006
- China
| | - Shaomin Shuang
- College of Chemistry and Chemical Engineering
- Shanxi University
- Taiyuan 030006
- China
| |
Collapse
|
13
|
Sirolimus induces depletion of intracellular calcium stores and mitochondrial dysfunction in pancreatic beta cells. Sci Rep 2017; 7:15823. [PMID: 29158477 PMCID: PMC5696524 DOI: 10.1038/s41598-017-15283-y] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Accepted: 10/20/2017] [Indexed: 12/19/2022] Open
Abstract
Sirolimus (rapamycin) is an immunosuppressive drug used in transplantation. One of its major side effects is the increased risk of diabetes mellitus; however, the exact mechanisms underlying such association have not been elucidated. Here we show that sirolimus impairs glucose-stimulated insulin secretion both in human and murine pancreatic islets and in clonal β cells in a dose- and time-dependent manner. Importantly, we demonstrate that sirolimus markedly depletes calcium (Ca2+) content in the endoplasmic reticulum and significantly decreases glucose-stimulated mitochondrial Ca2+ uptake. Crucially, the reduced mitochondrial Ca2+ uptake is mirrored by a significant impairment in mitochondrial respiration. Taken together, our findings indicate that sirolimus causes depletion of intracellular Ca2+ stores and alters mitochondrial fitness, eventually leading to decreased insulin release. Our results provide a novel molecular mechanism underlying the increased incidence of diabetes mellitus in patients treated with this drug.
Collapse
|
14
|
Sun J, Ling P, Gao F. A Mitochondria-Targeted Ratiometric Biosensor for pH Monitoring and Imaging in Living Cells with Congo-Red-Functionalized Dual-Emission Semiconducting Polymer Dots. Anal Chem 2017; 89:11703-11710. [DOI: 10.1021/acs.analchem.7b03154] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Junyong Sun
- Laboratory of Functionalized
Molecular Solids, Ministry of Education, Anhui Key Laboratory of Chemo/Biosensing,
Laboratory of Optical Probes and Bioelectrocatalysis (LOPAB), College
of Chemistry and Materials Science, Anhui Normal University, Wuhu 241000, P. R. China
| | - Pinghua Ling
- Laboratory of Functionalized
Molecular Solids, Ministry of Education, Anhui Key Laboratory of Chemo/Biosensing,
Laboratory of Optical Probes and Bioelectrocatalysis (LOPAB), College
of Chemistry and Materials Science, Anhui Normal University, Wuhu 241000, P. R. China
| | - Feng Gao
- Laboratory of Functionalized
Molecular Solids, Ministry of Education, Anhui Key Laboratory of Chemo/Biosensing,
Laboratory of Optical Probes and Bioelectrocatalysis (LOPAB), College
of Chemistry and Materials Science, Anhui Normal University, Wuhu 241000, P. R. China
| |
Collapse
|
15
|
Szabò I, Spetea C. Impact of the ion transportome of chloroplasts on the optimization of photosynthesis. JOURNAL OF EXPERIMENTAL BOTANY 2017; 68:3115-3128. [PMID: 28338935 DOI: 10.1093/jxb/erx063] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Ions play fundamental roles in all living cells, and their gradients are often essential to fuel transport, regulate enzyme activities, and transduce energy within cells. Regulation of their homeostasis is essential for cell metabolism. Recent results indicate that modulation of ion fluxes might also represent a useful strategy to regulate one of the most important physiological processes taking place in chloroplasts, photosynthesis. Photosynthesis is highly regulated, due to its unique role as a cellular engine for growth in the light. Controlling the balance between ATP and NADPH synthesis is a critical task, and availability of these molecules can limit the overall photosynthetic yield. Photosynthetic organisms optimize photosynthesis in low light, where excitation energy limits CO2 fixation, and minimize photo-oxidative damage in high light by dissipating excess photons. Despite extensive studies of these phenomena, the mechanism governing light utilization in plants is still poorly understood. In this review, we provide an update of the recently identified chloroplast-located ion channels and transporters whose function impacts photosynthetic efficiency in plants.
Collapse
Affiliation(s)
- Ildikò Szabò
- Department of Biology, University of Padova, Italy; CNR Institute of Neuroscience, Padova, Italy
| | - Cornelia Spetea
- Department of Biological and Environmental Sciences, University of Gothenburg, 40530 Gothenburg, Sweden
| |
Collapse
|
16
|
Abstract
The pancreatic β-cell secretes insulin in response to elevated plasma glucose. This review applies an external bioenergetic critique to the central processes of glucose-stimulated insulin secretion, including glycolytic and mitochondrial metabolism, the cytosolic adenine nucleotide pool, and its interaction with plasma membrane ion channels. The control mechanisms responsible for the unique responsiveness of the cell to glucose availability are discussed from bioenergetic and metabolic control standpoints. The concept of coupling factor facilitation of secretion is critiqued, and an attempt is made to unravel the bioenergetic basis of the oscillatory mechanisms controlling secretion. The need to consider the physiological constraints operating in the intact cell is emphasized throughout. The aim is to provide a coherent pathway through an extensive, complex, and sometimes bewildering literature, particularly for those unfamiliar with the field.
Collapse
Affiliation(s)
- David G Nicholls
- Buck Institute for Research on Aging, Novato, California; and Department of Clinical Sciences, Unit of Molecular Metabolism, Lund University Diabetes Centre, Malmo, Sweden
| |
Collapse
|
17
|
Leanza L, Romio M, Becker KA, Azzolini M, Trentin L, Managò A, Venturini E, Zaccagnino A, Mattarei A, Carraretto L, Urbani A, Kadow S, Biasutto L, Martini V, Severin F, Peruzzo R, Trimarco V, Egberts JH, Hauser C, Visentin A, Semenzato G, Kalthoff H, Zoratti M, Gulbins E, Paradisi C, Szabo I. Direct Pharmacological Targeting of a Mitochondrial Ion Channel Selectively Kills Tumor Cells In Vivo. Cancer Cell 2017; 31:516-531.e10. [PMID: 28399409 DOI: 10.1016/j.ccell.2017.03.003] [Citation(s) in RCA: 122] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 02/03/2017] [Accepted: 03/07/2017] [Indexed: 12/13/2022]
Abstract
The potassium channel Kv1.3 is highly expressed in the mitochondria of various cancerous cells. Here we show that direct inhibition of Kv1.3 using two mitochondria-targeted inhibitors alters mitochondrial function and leads to reactive oxygen species (ROS)-mediated death of even chemoresistant cells independently of p53 status. These inhibitors killed 98% of ex vivo primary chronic B-lymphocytic leukemia tumor cells while sparing healthy B cells. In orthotopic mouse models of melanoma and pancreatic ductal adenocarcinoma, the compounds reduced tumor size by more than 90% and 60%, respectively, while sparing immune and cardiac functions. Our work provides direct evidence that specific pharmacological targeting of a mitochondrial potassium channel can lead to ROS-mediated selective apoptosis of cancer cells in vivo, without causing significant side effects.
Collapse
Affiliation(s)
- Luigi Leanza
- Department of Biology, University of Padova, viale G. Colombo 3, 35121 Padova, Italy
| | - Matteo Romio
- Department of Chemical Sciences, University of Padova, via F. Marzolo 1, 35121 Padova, Italy
| | - Katrin Anne Becker
- Department of Molecular Biology, University of Duisburg-Essen, Hufelandstrasse 55, 45122 Essen, Germany
| | - Michele Azzolini
- Department of Biomedical Sciences, University of Padova, viale G. Colombo 3, 35121 Padova, Italy; CNR Institute of Neuroscience, viale G. Colombo 3, 35121 Padova, Italy
| | - Livio Trentin
- Department of Medicine, Hematology and Immunological Branch, University of Padova, and Venetian Institute for Molecular Medicine (VIMM), via G. Orus 2, 35129 Padova, Italy
| | - Antonella Managò
- Department of Biology, University of Padova, viale G. Colombo 3, 35121 Padova, Italy
| | - Elisa Venturini
- Department of Molecular Biology, University of Duisburg-Essen, Hufelandstrasse 55, 45122 Essen, Germany
| | - Angela Zaccagnino
- Institute for Experimental Cancer Research, Medical Faculty, CAU, Kiel, and Department of Surgery, UKSH, Campus Kiel, Arnold-Heller-Strasse 3 (Haus 17), 24105 Kiel, Germany
| | - Andrea Mattarei
- Department of Chemical Sciences, University of Padova, via F. Marzolo 1, 35121 Padova, Italy
| | - Luca Carraretto
- Department of Biology, University of Padova, viale G. Colombo 3, 35121 Padova, Italy
| | - Andrea Urbani
- Department of Biology, University of Padova, viale G. Colombo 3, 35121 Padova, Italy
| | - Stephanie Kadow
- Department of Molecular Biology, University of Duisburg-Essen, Hufelandstrasse 55, 45122 Essen, Germany
| | - Lucia Biasutto
- Department of Biomedical Sciences, University of Padova, viale G. Colombo 3, 35121 Padova, Italy; CNR Institute of Neuroscience, viale G. Colombo 3, 35121 Padova, Italy
| | - Veronica Martini
- Department of Medicine, Hematology and Immunological Branch, University of Padova, and Venetian Institute for Molecular Medicine (VIMM), via G. Orus 2, 35129 Padova, Italy
| | - Filippo Severin
- Department of Medicine, Hematology and Immunological Branch, University of Padova, and Venetian Institute for Molecular Medicine (VIMM), via G. Orus 2, 35129 Padova, Italy
| | - Roberta Peruzzo
- Department of Biology, University of Padova, viale G. Colombo 3, 35121 Padova, Italy
| | - Valentina Trimarco
- Department of Medicine, Hematology and Immunological Branch, University of Padova, and Venetian Institute for Molecular Medicine (VIMM), via G. Orus 2, 35129 Padova, Italy
| | - Jan-Hendrik Egberts
- Institute for Experimental Cancer Research, Medical Faculty, CAU, Kiel, and Department of Surgery, UKSH, Campus Kiel, Arnold-Heller-Strasse 3 (Haus 17), 24105 Kiel, Germany
| | - Charlotte Hauser
- Institute for Experimental Cancer Research, Medical Faculty, CAU, Kiel, and Department of Surgery, UKSH, Campus Kiel, Arnold-Heller-Strasse 3 (Haus 17), 24105 Kiel, Germany
| | - Andrea Visentin
- Department of Medicine, Hematology and Immunological Branch, University of Padova, and Venetian Institute for Molecular Medicine (VIMM), via G. Orus 2, 35129 Padova, Italy
| | - Gianpietro Semenzato
- Department of Medicine, Hematology and Immunological Branch, University of Padova, and Venetian Institute for Molecular Medicine (VIMM), via G. Orus 2, 35129 Padova, Italy
| | - Holger Kalthoff
- Institute for Experimental Cancer Research, Medical Faculty, CAU, Kiel, and Department of Surgery, UKSH, Campus Kiel, Arnold-Heller-Strasse 3 (Haus 17), 24105 Kiel, Germany
| | - Mario Zoratti
- Department of Biomedical Sciences, University of Padova, viale G. Colombo 3, 35121 Padova, Italy; CNR Institute of Neuroscience, viale G. Colombo 3, 35121 Padova, Italy
| | - Erich Gulbins
- Department of Molecular Biology, University of Duisburg-Essen, Hufelandstrasse 55, 45122 Essen, Germany; Department of Surgery, University of Cincinnati, 231 Albert Sabin Way, Cincinnati, OH 45267-0558, USA.
| | - Cristina Paradisi
- Department of Chemical Sciences, University of Padova, via F. Marzolo 1, 35121 Padova, Italy.
| | - Ildiko Szabo
- Department of Biology, University of Padova, viale G. Colombo 3, 35121 Padova, Italy; CNR Institute of Neuroscience, viale G. Colombo 3, 35121 Padova, Italy.
| |
Collapse
|
18
|
Feng G, Liu B, Hou T, Wang X, Cheng H. Mitochondrial Flashes: Elemental Signaling Events in Eukaryotic Cells. Handb Exp Pharmacol 2017; 240:403-422. [PMID: 28233181 DOI: 10.1007/164_2016_129] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Mitochondrial flashes (mitoflashes) are recently discovered mitochondrial activity which reflects chemical and electrical excitation of the organelle. Emerging evidence indicates that mitoflashes represent highly regulated, elementary signaling events that play important roles in physiological and pathophysiological processes in eukaryotes. Furthermore, they are regulated by mitochondrial ROS, Ca2+, and protons, and are intertwined with mitochondrial metabolic processes. As such, targeting mitoflash activity may provide a novel means for the control of mitochondrial metabolism and signaling in health and disease. In this brief review, we summarize salient features and mechanisms of biogenesis of mitoflashes, and synthesize data on mitoflash biology in the context of metabolism, cell differentiation, stress response, disease, and ageing.
Collapse
Affiliation(s)
- Gaomin Feng
- Institute of Molecular Medicine, Peking University, Beijing, 100871, China
| | - Beibei Liu
- Institute of Molecular Medicine, Peking University, Beijing, 100871, China
| | - Tingting Hou
- Institute of Molecular Medicine, Peking University, Beijing, 100871, China
| | - Xianhua Wang
- Institute of Molecular Medicine, Peking University, Beijing, 100871, China
| | - Heping Cheng
- Institute of Molecular Medicine, Peking University, Beijing, 100871, China.
| |
Collapse
|
19
|
Nita II, Caspi Y, Gudes S, Fishman D, Lev S, Hersfinkel M, Sekler I, Binshtok AM. Privileged crosstalk between TRPV1 channels and mitochondrial calcium shuttling machinery controls nociception. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:2868-2880. [DOI: 10.1016/j.bbamcr.2016.09.009] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Revised: 09/06/2016] [Accepted: 09/09/2016] [Indexed: 10/21/2022]
|
20
|
Cao L, Zhao Z, Zhang T, Guo X, Wang S, Li S, Li Y, Yang G. In vivo observation of the pH alternation in mitochondria for various external stimuli. Chem Commun (Camb) 2016; 51:17324-7. [PMID: 26462552 DOI: 10.1039/c5cc07118f] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The pH of mitochondria (pHm) has a close relationship with many biological processes. Here we developed a new indicator Mito-pH-1 for the ratiometric fluorescence detection of the mitochondria pH value, which has excellent tolerance to environmental change. And Mito-pH-1 has been used for the first time to monitor the change of pHm under temperature and H2O2 stimuli in living cells.
Collapse
Affiliation(s)
- Lixia Cao
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
| | - Zhensheng Zhao
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
| | - Tao Zhang
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
| | - Xudong Guo
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
| | - Shuangqing Wang
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
| | - Shayu Li
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
| | - Yi Li
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
| | - Guoqiang Yang
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
| |
Collapse
|
21
|
Gerencser AA, Mookerjee SA, Jastroch M, Brand MD. Measurement of the Absolute Magnitude and Time Courses of Mitochondrial Membrane Potential in Primary and Clonal Pancreatic Beta-Cells. PLoS One 2016; 11:e0159199. [PMID: 27404273 PMCID: PMC4942067 DOI: 10.1371/journal.pone.0159199] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 06/28/2016] [Indexed: 12/22/2022] Open
Abstract
The aim of this study was to simplify, improve and validate quantitative measurement of the mitochondrial membrane potential (ΔψM) in pancreatic β-cells. This built on our previously introduced calculation of the absolute magnitude of ΔψM in intact cells, using time-lapse imaging of the non-quench mode fluorescence of tetramethylrhodamine methyl ester and a bis-oxonol plasma membrane potential (ΔψP) indicator. ΔψM is a central mediator of glucose-stimulated insulin secretion in pancreatic β-cells. ΔψM is at the crossroads of cellular energy production and demand, therefore precise assay of its magnitude is a valuable tool to study how these processes interplay in insulin secretion. Dispersed islet cell cultures allowed cell type-specific, single-cell observations of cell-to-cell heterogeneity of ΔψM and ΔψP. Glucose addition caused hyperpolarization of ΔψM and depolarization of ΔψP. The hyperpolarization was a monophasic step increase, even in cells where the ΔψP depolarization was biphasic. The biphasic response of ΔψP was associated with a larger hyperpolarization of ΔψM than the monophasic response. Analysis of the relationships between ΔψP and ΔψM revealed that primary dispersed β-cells responded to glucose heterogeneously, driven by variable activation of energy metabolism. Sensitivity analysis of the calibration was consistent with β-cells having substantial cell-to-cell variations in amounts of mitochondria, and this was predicted not to impair the accuracy of determinations of relative changes in ΔψM and ΔψP. Finally, we demonstrate a significant problem with using an alternative ΔψM probe, rhodamine 123. In glucose-stimulated and oligomycin-inhibited β-cells the principles of the rhodamine 123 assay were breached, resulting in misleading conclusions.
Collapse
Affiliation(s)
- Akos A. Gerencser
- Buck Institute for Research on Aging, Novato, California, United States of America
- Image Analyst Software, Novato, California, United States of America
| | - Shona A. Mookerjee
- Buck Institute for Research on Aging, Novato, California, United States of America
- Touro University California College of Pharmacy, Vallejo, California, United States of America
| | - Martin Jastroch
- Buck Institute for Research on Aging, Novato, California, United States of America
| | - Martin D. Brand
- Buck Institute for Research on Aging, Novato, California, United States of America
| |
Collapse
|
22
|
Speract, a sea urchin egg peptide that regulates sperm motility, also stimulates sperm mitochondrial metabolism. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1857:415-26. [PMID: 26772728 DOI: 10.1016/j.bbabio.2016.01.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 08/01/2015] [Revised: 12/22/2015] [Accepted: 01/05/2016] [Indexed: 11/21/2022]
Abstract
Sea urchin sperm have only one mitochondrion, that in addition to being the main source of energy, may modulate intracellular Ca(2+) concentration ([Ca(2+)]i) to regulate their motility and possibly the acrosome reaction. Speract is a decapeptide from the outer jelly layer of the Strongylocentrotus purpuratus egg that upon binding to its receptor in the sperm, stimulates sperm motility, respiration and ion fluxes, among other physiological events. Altering the sea urchin sperm mitochondrial function with specific inhibitors of this organelle, increases [Ca(2+)]i in an external Ca(2+) concentration ([Ca(2+)]ext)-dependent manner (Ardón, et al., 2009. BBActa 1787: 15), suggesting that the mitochondrion is involved in sperm [Ca(2+)]i homeostasis. To further understand the interrelationship between the mitochondrion and the speract responses, we measured mitochondrial membrane potential (ΔΨ) and NADH levels. We found that the stimulation of sperm with speract depolarizes the mitochondrion and increases the levels of NADH. Surprisingly, these responses are independent of external Ca(2+) and are due to the increase in intracellular pH (pHi) induced by speract. Our findings indicate that speract, by regulating pHi, in addition to [Ca(2+)]i, may finely modulate mitochondrial metabolism to control motility and ensure that sperm reach the egg and fertilize it.
Collapse
|
23
|
Early effects of the antineoplastic agent salinomycin on mitochondrial function. Cell Death Dis 2015; 6:e1930. [PMID: 26492365 PMCID: PMC4632293 DOI: 10.1038/cddis.2015.263] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Revised: 07/10/2015] [Accepted: 08/03/2015] [Indexed: 02/07/2023]
Abstract
Salinomycin, isolated from Streptomyces albus, displays antimicrobial activity. Recently, a large-scale screening approach identified salinomycin and nigericin as selective apoptosis inducers of cancer stem cells. Growing evidence suggests that salinomycin is able to kill different types of non-stem tumor cells that usually display resistance to common therapeutic approaches, but the mechanism of action of this molecule is still poorly understood. Since salinomycin has been suggested to act as a K(+) ionophore, we explored its impact on mitochondrial bioenergetic performance at an early time point following drug application. In contrast to the K(+) ionophore valinomycin, salinomycin induced a rapid hyperpolarization. In addition, mitochondrial matrix acidification and a significant decrease of respiration were observed in intact mouse embryonic fibroblasts (MEFs) and in cancer stem cell-like HMLE cells within tens of minutes, while increased production of reactive oxygen species was not detected. By comparing the chemical structures and cellular effects of this drug with those of valinomycin (K(+) ionophore) and nigericin (K(+)/H(+) exchanger), we conclude that salinomycin mediates K(+)/H(+) exchange across the inner mitochondrial membrane. Compatible with its direct modulation of mitochondrial function, salinomycin was able to induce cell death also in Bax/Bak-less double-knockout MEF cells. Since at the concentration range used in most studies (around 10 μM) salinomycin exerts its effect at the level of mitochondria and alters bioenergetic performance, the specificity of its action on pathologic B cells isolated from patients with chronic lymphocytic leukemia (CLL) versus B cells from healthy subjects was investigated. Mesenchymal stromal cells (MSCs), proposed to mimic the tumor environment, attenuated the apoptotic effect of salinomycin on B-CLL cells. Apoptosis occurred to a significant extent in healthy B cells as well as in MSCs and human primary fibroblasts. The results indicate that salinomycin, when used above μM concentrations, exerts direct, mitochondrial effects, thus compromising cell survival.
Collapse
|
24
|
Dahal E, Curtiss J, Subedi D, Chen G, Houston JP, Smirnov S. Evaluation of the catalytic activity and cytotoxicity of palladium nanocubes: the role of oxygen. ACS APPLIED MATERIALS & INTERFACES 2015; 7:9364-71. [PMID: 25886644 PMCID: PMC4663053 DOI: 10.1021/am509124x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Recently, it has been reported that palladium nanocubes (PdNC) are capable of generating singlet oxygen without photoexcitation simply via chemisorption of molecular oxygen on its surface. Such a trait would make PdNC a highly versatile catalyst suitable in organic synthesis and a Reactive Oxygen Species (ROS) inducing cancer treatment reagent. Here we thoroughly investigated the catalytic activity of PdNC with respect to their ability to produce singlet oxygen and to oxidize 3,3',5,5'-tetramethylbenzidine (TMB), and analyzed the cytotoxic properties of PdNC on HeLa cells. Our findings showed no evidence of singlet oxygen production by PdNC. The nanocubes' activity is not necessarily linked to activation of oxygen. The oxidation of substrate on PdNC can be a first step, followed by PdNC regeneration with oxygen or other oxidant. The catalytic activity of PdNC toward the oxidation of TMB is very high and shows direct two-electron oxidation when the surface of the PdNC is clean and the ratio of TMB/PdNC is not very high. Sequential one electron oxidation is observed when the pristine quality of PdNC surface is compromised by serum or uncontrolled impurities and/or the ratio of TMB/PdNC is high. Clean PdNC in serum-free media efficiently induce apoptosis of HeLa cells. It is the primary route of cell death and is associated with hyperpolarization of mitochondria, contrary to a common mitochondrial depolarization initiated by ROS. Again, the effects are very sensitive to how well the pristine surface of PdNC is preserved, suggesting that PdNC can be used as an apoptosis inducing agent, but only with appropriate drug delivery system.
Collapse
Affiliation(s)
- Eshan Dahal
- Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, New Mexico 88003, United States
| | - Jessica Curtiss
- Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, New Mexico 88003, United States
| | - Deepak Subedi
- Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, New Mexico 88003, United States
| | - Gen Chen
- Department of Chemical Engineering, New Mexico State University, Las Cruces, New Mexico 88003, United States
| | - Jessica P. Houston
- Department of Chemical Engineering, New Mexico State University, Las Cruces, New Mexico 88003, United States
| | - Sergei Smirnov
- Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, New Mexico 88003, United States
| |
Collapse
|
25
|
Mitochondrial Ca2+-dependent NLRP3 activation exacerbates the Pseudomonas aeruginosa-driven inflammatory response in cystic fibrosis. Nat Commun 2015; 6:6201. [PMID: 25648527 DOI: 10.1038/ncomms7201] [Citation(s) in RCA: 117] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 01/05/2015] [Indexed: 12/28/2022] Open
Abstract
The common pathological manifestation of cystic fibrosis (CF) is associated with an excessive lung inflammatory response characterized by interleukin-1β accumulation. CF airway epithelial cells show an exacerbated pro-inflammatory response to Pseudomonas aeruginosa; however, it is unclear whether this heightened inflammatory response is intrinsic to cells lacking CF transmembrane conductance regulator (CFTR). Here we demonstrate that the degree and quality of the inflammatory response in CF are supported by P. aeruginosa-dependent mitochondrial perturbation, in which flagellin is the inducer and mitochondrial Ca(2+) uniporter (MCU) is a signal-integrating organelle member for NLRP3 activation and IL-1β and IL-18 processing. Our work elucidates the regulation of the NLRP3 inflammasome by mitochondrial Ca(2+) in the P. aeruginosa-dependent inflammatory response and deepens our understanding of the significance of mitochondria in the Ca(2+)-dependent control of inflammation.
Collapse
|
26
|
Quan X, Nguyen TT, Choi SK, Xu S, Das R, Cha SK, Kim N, Han J, Wiederkehr A, Wollheim CB, Park KS. Essential role of mitochondrial Ca2+ uniporter in the generation of mitochondrial pH gradient and metabolism-secretion coupling in insulin-releasing cells. J Biol Chem 2014; 290:4086-96. [PMID: 25548283 DOI: 10.1074/jbc.m114.632547] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
In pancreatic β-cells, ATP acts as a signaling molecule initiating plasma membrane electrical activity linked to Ca(2+) influx, which triggers insulin exocytosis. The mitochondrial Ca(2+) uniporter (MCU) mediates Ca(2+) uptake into the organelle, where energy metabolism is further stimulated for sustained second phase insulin secretion. Here, we have studied the contribution of the MCU to the regulation of oxidative phosphorylation and metabolism-secretion coupling in intact and permeabilized clonal β-cells as well as rat pancreatic islets. Knockdown of MCU with siRNA transfection blunted matrix Ca(2+) rises, decreased nutrient-stimulated ATP production as well as insulin secretion. Furthermore, MCU knockdown lowered the expression of respiratory chain complexes, mitochondrial metabolic activity, and oxygen consumption. The pH gradient formed across the inner mitochondrial membrane following nutrient stimulation was markedly lowered in MCU-silenced cells. In contrast, nutrient-induced hyperpolarization of the electrical gradient was not altered. In permeabilized cells, knockdown of MCU ablated matrix acidification in response to extramitochondrial Ca(2+). Suppression of the putative Ca(2+)/H(+) antiporter leucine zipper-EF hand-containing transmembrane protein 1 (LETM1) also abolished Ca(2+)-induced matrix acidification. These results demonstrate that MCU-mediated Ca(2+) uptake is essential to establish a nutrient-induced mitochondrial pH gradient which is critical for sustained ATP synthesis and metabolism-secretion coupling in insulin-releasing cells.
Collapse
Affiliation(s)
- Xianglan Quan
- From the Department of Physiology, Yonsei University Wonju College of Medicine, Wonju, Gangwon-Do 220-701, Korea
| | - Tuyet Thi Nguyen
- From the Department of Physiology, Yonsei University Wonju College of Medicine, Wonju, Gangwon-Do 220-701, Korea
| | - Seong-Kyung Choi
- From the Department of Physiology, Yonsei University Wonju College of Medicine, Wonju, Gangwon-Do 220-701, Korea
| | - Shanhua Xu
- From the Department of Physiology, Yonsei University Wonju College of Medicine, Wonju, Gangwon-Do 220-701, Korea
| | - Ranjan Das
- From the Department of Physiology, Yonsei University Wonju College of Medicine, Wonju, Gangwon-Do 220-701, Korea
| | - Seung-Kuy Cha
- From the Department of Physiology, Yonsei University Wonju College of Medicine, Wonju, Gangwon-Do 220-701, Korea
| | - Nari Kim
- Department of Physiology, College of Medicine, Inje University, Busan 614-735, Korea
| | - Jin Han
- Department of Physiology, College of Medicine, Inje University, Busan 614-735, Korea
| | | | - Claes B Wollheim
- Department of Cell Physiology and Metabolism, University of Geneva, 1211 Geneva 4, Switzerland
| | - Kyu-Sang Park
- From the Department of Physiology, Yonsei University Wonju College of Medicine, Wonju, Gangwon-Do 220-701, Korea,
| |
Collapse
|
27
|
A crosstalk between Na⁺ channels, Na⁺/K⁺ pump and mitochondrial Na⁺ transporters controls glucose-dependent cytosolic and mitochondrial Na⁺ signals. Cell Calcium 2014; 57:69-75. [PMID: 25564413 DOI: 10.1016/j.ceca.2014.12.007] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Revised: 12/09/2014] [Accepted: 12/10/2014] [Indexed: 11/22/2022]
Abstract
Glucose-dependent cytosolic Na(+) influx in pancreatic islet β cells is mediated by TTX-sensitive Na(+) channels and is propagated into the mitochondria through the mitochondrial Na(+)/Ca(2+) exchanger, NCLX. Mitochondrial Na(+) transients are also controlled by the mitochondrial Na(+)/H(+) exchanger, NHE, while cytosolic Na(+) changes are governed by Na(+)/K(+) ATPase pump. The functional interaction between the Na(+) channels, Na(+)/K(+) ATPase pump and mitochondrial Na(+) transporters, NCLX and NHE, in mediating Na(+) signaling is poorly understood. Here, we combine fluorescent Na(+) imaging, pharmacological inhibition by TTX, ouabain and EIPA, with molecular control of NCLX expression, so as to investigate the crosstalk between Na(+) transporters on both the plasma membrane and the mitochondria. According to our results, glucose-dependent cytosolic Na(+) response was enhanced by ouabain and was followed by a rise in mitochondrial Na(+) signal. Silencing of NCLX expression using siNCLX, did not affect the glucose- or ouabain-dependent cytosolic rise in Na(+). In contrast, the ouabain-dependent rise in mitochondrial Na(+) was strongly suppressed by siNCLX. Furthermore, mitochondrial Na(+) influx rates were accelerated in cells treated with the Na(+)/H(+) exchanger inhibitor, EIPA or by combination of EIPA and ouabain. Similarly, TTX blocked the cytosolic and mitochondrial Na(+) responses, which were enhanced by ouabain or EIPA, respectively. Our results suggest that Na(+)/K(+) ATPase pump controls cytosolic glucose-dependent Na(+) rise, in a manner that is mediated by TTX-sensitive Na(+) channels and subsequent mitochondrial Na(+) uptake via NCLX. Furthermore, these results indicate that mitochondrial Na(+) influx via NCLX is antagonized by Na(+) efflux, which is mediated by the mitochondrial NHE; thus, the duration of mitochondrial Na(+) transients is set by the interplay between these pivotal transporters.
Collapse
|
28
|
Chabosseau P, Tuncay E, Meur G, Bellomo EA, Hessels A, Hughes S, Johnson PRV, Bugliani M, Marchetti P, Turan B, Lyon AR, Merkx M, Rutter GA. Mitochondrial and ER-targeted eCALWY probes reveal high levels of free Zn2+. ACS Chem Biol 2014; 9:2111-20. [PMID: 25011072 PMCID: PMC6101202 DOI: 10.1021/cb5004064] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Zinc (Zn2+) ions are increasingly recognized as playing an important role in cellular physiology. Whereas the free Zn2+ concentration in the cytosol has been established to be 0.1-1 nM, the free Zn2+ concentration in subcellular organelles is not well-established. Here, we extend the eCALWY family of genetically encoded Förster Resonance Energy Transfer (FRET) Zn2+ probes to permit measurements in the endo(sarco)plasmic reticulum (ER) and mitochondrial matrix. Deployed in a variety of mammalian cell types, these probes reveal resting mitochondrial free [Zn2+] values of ∼300 pM, somewhat lower than in the cytosol but 3 orders of magnitude higher than recently reported using an alternative FRET-based sensor. By contrast, free ER [Zn2+] was found to be ≥5 nM, which is >5000-fold higher than recently reported but consistent with the proposed role of the ER as a mobilizable Zn2+ store. Treatment of β-cells or cardiomyocytes with sarco(endo)plasmic reticulum Ca2+-ATPase inhibitors, mobilization of ER Ca2+ after purinergic stimulation with ATP, or manipulation of ER redox, exerted no detectable effects on [Zn2+]ER. These findings question the previously proposed role of Ca2+ in Zn2+ mobilization from the ER and suggest that high ER Zn2+ levels may be an important aspect of cellular homeostasis.
Collapse
Affiliation(s)
- Pauline Chabosseau
- Section of Cell Biology, Division of Medicine, and ‡National Heart and Lung Institute, Imperial College London , London, United Kingdom
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
29
|
Nita II, Hershfinkel M, Kantor C, Rutter GA, Lewis EC, Sekler I. Pancreatic β-cell Na+ channels control global Ca2+ signaling and oxidative metabolism by inducing Na+ and Ca2+ responses that are propagated into mitochondria. FASEB J 2014; 28:3301-12. [PMID: 24719357 DOI: 10.1096/fj.13-248161] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Communication between the plasma membrane and mitochondria is essential for initiating the Ca(2+) and metabolic signals required for secretion in β cells. Although voltage-dependent Na(+) channels are abundantly expressed in β cells and activated by glucose, their role in communicating with mitochondria is unresolved. Here, we combined fluorescent Na(+), Ca(2+), and ATP imaging, electrophysiological analysis with tetrodotoxin (TTX)-dependent block of the Na(+) channel, and molecular manipulation of mitochondrial Ca(2+) transporters to study the communication between Na(+) channels and mitochondria. We show that TTX inhibits glucose-dependent depolarization and blocks cytosolic Na(+) and Ca(2+) responses and their propagation into mitochondria. TTX-sensitive mitochondrial Ca(2+) influx was largely blocked by knockdown of the mitochondrial Ca(2+) uniporter (MCU) expression. Knockdown of the mitochondrial Na(+)/Ca(2+) exchanger (NCLX) and Na(+) dose response analysis demonstrated that NCLX mediates the mitochondrial Na(+) influx and is tuned to sense the TTX-sensitive cytosolic Na(+) responses. Finally, TTX blocked glucose-dependent mitochondrial Ca(2+) rise, mitochondrial metabolic activity, and ATP production. Our results show that communication of the Na(+) channels with mitochondria shape both global Ca(2+) and metabolism signals linked to insulin secretion in β cells.- Nita, I. I., Hershfinkel, M., Kantor, C., Rutter, G. A., Lewis, E. C., Sekler, I. Pancreatic β-cell Na(+) channels control global Ca(2+) signaling and oxidative metabolism by inducing Na(+) and Ca(2+) responses that are propagated into mitochondria.
Collapse
Affiliation(s)
| | | | - Chase Kantor
- Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine, Imperial College London, London, UK
| | - Guy A Rutter
- Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine, Imperial College London, London, UK
| | - Eli C Lewis
- Department of Clinical Biochemistry, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel; and
| | | |
Collapse
|
30
|
Silverstein TP. An exploration of how the thermodynamic efficiency of bioenergetic membrane systems varies with c-subunit stoichiometry of F₁F₀ ATP synthases. J Bioenerg Biomembr 2014; 46:229-41. [PMID: 24706236 DOI: 10.1007/s10863-014-9547-y] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Accepted: 02/24/2014] [Indexed: 10/25/2022]
Abstract
Recently the F0 portion of the bovine mitochondrial F1F0-ATP synthase was shown to contain eight 'c' subunits (n = 8). This surprised many in the field, as previously, the only other mitochondrial F0 (for yeast) was shown to have ten 'c' subunits. The metabolic implications of 'c' subunit copy number explored in this paper lead to several surprising conclusions: (1) Aerobically respiring E. coli (n = 10) and animal mitochondria (n = 8) both have very high F1F0 thermodynamic efficiencies of ≈90% under typical conditions, whereas efficiency is only ≈65% for chloroplasts (n = 14). Reasons for this difference, including the importance of transmembrane potential (∆Ψ) as a rotational catalyst, as opposed to an energy source, are discussed. (2) Maximum theoretical P/O ratios in animal mitochondria (n = 8) are calculated to be 2.73 ATP/NADH and 1.64 ATP/FADH2, yielding 34.5 ATP/glucose (assuming NADH import via the malate/aspartate shuttle). The experimentally measured values of 2.44 (±0.15), 1.47 (±0.13), and 31.3 (±1.5), respectively, are only about 10% lower, suggesting very little energy depletion via transmembrane proton leakage. (3) Finally, the thermodynamic efficiency of oxidative phosphorylation is not lower than that of substrate level phosphorylation, as previously believed. The overall thermodynamic efficiencies of oxidative phosphorylation, glycolysis, and the citric acid cycle are ≈80% in all three processes.
Collapse
|
31
|
De Marchi U, Thevenet J, Hermant A, Dioum E, Wiederkehr A. Calcium co-regulates oxidative metabolism and ATP synthase-dependent respiration in pancreatic beta cells. J Biol Chem 2014; 289:9182-94. [PMID: 24554722 PMCID: PMC3979381 DOI: 10.1074/jbc.m113.513184] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Mitochondrial energy metabolism is essential for glucose-induced calcium signaling and, therefore, insulin granule exocytosis in pancreatic beta cells. Calcium signals are sensed by mitochondria acting in concert with mitochondrial substrates for the full activation of the organelle. Here we have studied glucose-induced calcium signaling and energy metabolism in INS-1E insulinoma cells and human islet beta cells. In insulin secreting cells a surprisingly large fraction of total respiration under resting conditions is ATP synthase-independent. We observe that ATP synthase-dependent respiration is markedly increased after glucose stimulation. Glucose also causes a very rapid elevation of oxidative metabolism as was followed by NAD(P)H autofluorescence. However, neither the rate of the glucose-induced increase nor the new steady-state NAD(P)H levels are significantly affected by calcium. Our findings challenge the current view, which has focused mainly on calcium-sensitive dehydrogenases as the target for the activation of mitochondrial energy metabolism. We propose a model of tight calcium-dependent regulation of oxidative metabolism and ATP synthase-dependent respiration in beta cell mitochondria. Coordinated activation of matrix dehydrogenases and respiratory chain activity by calcium allows the respiratory rate to change severalfold with only small or no alterations of the NAD(P)H/NAD(P)(+) ratio.
Collapse
|
32
|
Wu H, Yin JJ, Wamer WG, Zeng M, Lo YM. Reactive oxygen species-related activities of nano-iron metal and nano-iron oxides. J Food Drug Anal 2014; 22:86-94. [PMID: 24673906 PMCID: PMC9359154 DOI: 10.1016/j.jfda.2014.01.007] [Citation(s) in RCA: 124] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Revised: 12/19/2013] [Accepted: 12/21/2013] [Indexed: 01/17/2023] Open
Abstract
Nano-iron metal and nano-iron oxides are among the most widely used engineered and naturally occurring nanostructures, and the increasing incidence of biological exposure to these nanostructures has raised concerns about their biotoxicity. Reactive oxygen species (ROS)-induced oxidative stress is one of the most accepted toxic mechanisms and, in the past decades, considerable efforts have been made to investigate the ROS-related activities of iron nanostructures. In this review, we summarize activities of nano-iron metal and nano-iron oxides in ROS-related redox processes, addressing in detail the known homogeneous and heterogeneous redox mechanisms involved in these processes, intrinsic ROS-related properties of iron nanostructures (chemical composition, particle size, and crystalline phase), and ROS-related bio-microenvironmental factors, including physiological pH and buffers, biogenic reducing agents, and other organic substances.
Collapse
Affiliation(s)
- Haohao Wu
- College of Food Science and Engineering, Ocean University of China, 5 Yushan Road, Qingdao, Shandong Province 266003, China; Department of Nutrition and Food Science, University of Maryland, College Park, MD 20742, USA; Center for Food Safety and Applied Nutrition, US Food and Drug Administration, College Park, MD 20740, USA
| | - Jun-Jie Yin
- Center for Food Safety and Applied Nutrition, US Food and Drug Administration, College Park, MD 20740, USA.
| | - Wayne G Wamer
- Center for Food Safety and Applied Nutrition, US Food and Drug Administration, College Park, MD 20740, USA
| | - Mingyong Zeng
- College of Food Science and Engineering, Ocean University of China, 5 Yushan Road, Qingdao, Shandong Province 266003, China
| | - Y Martin Lo
- Department of Nutrition and Food Science, University of Maryland, College Park, MD 20742, USA
| |
Collapse
|
33
|
Groschner LN, Alam MR, Graier WF. Metabolism-secretion coupling and mitochondrial calcium activities in clonal pancreatic β-cells. VITAMINS AND HORMONES 2014; 95:63-86. [PMID: 24559914 DOI: 10.1016/b978-0-12-800174-5.00003-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Pancreatic β-cells are the only cells capable of lowering blood glucose by secreting insulin. The β-cell continuously adjusts its secretory activity to substrate availability in order to keep blood glucose levels within the physiological range--a process called metabolism-secretion coupling. Glucose is readily taken up by the β-cell and broken down into intermediates that fuel oxidative metabolism inside the mitochondria to generate ATP. The resulting increase in the ATP/ADP ratio causes closure of plasma membrane KATP channels, thereby depolarizing the cell and triggering the opening of voltage-gated Ca²⁺ channels. Consequential oscillations of cytosolic Ca²⁺ not only mediate the exocytosis of insulin granules but are also relayed to other subcellular compartments including the mitochondria, where Ca²⁺ is required to accelerate mitochondrial metabolism in response to nutrient stimulation. The mitochondrial Ca²⁺ uptake machinery plays a fundamental role in this feed-forward mechanism that guarantees sustained insulin secretion and, thus, represents a promising therapeutic target for type 2 diabetes.
Collapse
Affiliation(s)
- Lukas N Groschner
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Graz, Austria
| | - Muhammad Rizwan Alam
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Graz, Austria
| | - Wolfgang F Graier
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Graz, Austria.
| |
Collapse
|
34
|
Trudeau KM, Gottlieb RA, Shirihai OS. Measurement of mitochondrial turnover and life cycle using MitoTimer. Methods Enzymol 2014; 547:21-38. [PMID: 25416350 DOI: 10.1016/b978-0-12-801415-8.00002-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Current methodologies available to quantify changes in mitochondrial turnover are limited to pulse-chase assays or specific assays that quantify mitophagy. Accordingly, new tools that can assess mitochondrial turnover are needed for the study of cellular, subcellular, and spatial parameters of mitochondrial turnover and quality control. Recently, a group of studies described the use of the MitoTimer fluorescent probe to investigate various aspects of mitochondrial turnover, including changes to protein import, interorganelle protein sharing, and autophagy-mediated turnover. MitoTimer provides a fluorescent readout which directly relates to the mitochondrial turnover rate and allows quantification of relative changes to turnover. Importantly, MitoTimer can be used to investigate mitochondrial turnover on the subcellular level. Due to the fact that MitoTimer is a dual-emission probe and a number of factors can affect MitoTimer readout, certain considerations must be taken into account when using this tool both in experimental design and data interpretation. When used and interpreted appropriately, MitoTimer serves as a unique tool to understand pivotal aspects of mitochondrial turnover.
Collapse
Affiliation(s)
- Kyle M Trudeau
- Department of Medicine, Obesity and Nutrition Section, The Mitochondria Affinity Research Collaborative, Evans Biomedical Research Center, Boston University School of Medicine, Boston, Massachusetts, USA
| | - Roberta A Gottlieb
- Department of Molecular Cardiobiology, Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Orian S Shirihai
- Department of Medicine, Obesity and Nutrition Section, The Mitochondria Affinity Research Collaborative, Evans Biomedical Research Center, Boston University School of Medicine, Boston, Massachusetts, USA; Department of Clinical Biochemistry and Pharmacology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Be'er-Sheva, Israel.
| |
Collapse
|
35
|
Quan X, Das R, Xu S, Cline GW, Wiederkehr A, Wollheim CB, Park KS. Mitochondrial phosphate transport during nutrient stimulation of INS-1E insulinoma cells. Mol Cell Endocrinol 2013; 381:198-209. [PMID: 23939247 DOI: 10.1016/j.mce.2013.08.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Revised: 07/18/2013] [Accepted: 08/03/2013] [Indexed: 11/15/2022]
Abstract
Here, we have investigated the role of inorganic phosphate (Pi) transport in mitochondria of rat clonal β-cells. In α-toxin-permeabilized INS-1E cells, succinate and glycerol-3-phosphate increased mitochondrial ATP release which depends on exogenous ADP and Pi. In the presence of substrates, addition of Pi caused mitochondrial matrix acidification and hyperpolarisation which promoted ATP export. Dissipation of the mitochondrial pH gradient or pharmacological inhibition of Pi transport blocked the effects of Pi on electrochemical gradient and ATP export. Knock-down of the phosphate transporter PiC, however, neither prevented Pi-induced mitochondrial activation nor glucose-induced insulin secretion. Using (31)P NMR we observed reduction of Pi pools during nutrient stimulation of INS-1E cells. Interestingly, Pi loss was less pronounced in mitochondria than in the cytosol. We conclude that matrix alkalinisation is necessary to maintain a mitochondrial Pi pool, at levels sufficient to stimulate energy metabolism in insulin-secreting cells beyond its role as a substrate for ATP synthesis.
Collapse
Affiliation(s)
- Xianglan Quan
- Department of Physiology and Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea
| | | | | | | | | | | | | |
Collapse
|
36
|
Ferree AW, Trudeau K, Zik E, Benador IY, Twig G, Gottlieb RA, Shirihai OS. MitoTimer probe reveals the impact of autophagy, fusion, and motility on subcellular distribution of young and old mitochondrial protein and on relative mitochondrial protein age. Autophagy 2013; 9:1887-96. [PMID: 24149000 PMCID: PMC4028338 DOI: 10.4161/auto.26503] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Revised: 09/09/2013] [Accepted: 09/16/2013] [Indexed: 12/02/2022] Open
Abstract
To study mitochondrial protein age dynamics, we targeted a time-sensitive fluorescent protein, MitoTimer, to the mitochondrial matrix. Mitochondrial age was revealed by the integrated portions of young (green) and old (red) MitoTimer protein. Mitochondrial protein age was dependent on turnover rates as pulsed synthesis, decreased import, or autophagic inhibition all increased the proportion of aged MitoTimer protein. Mitochondrial fusion promotes the distribution of young mitochondrial protein across the mitochondrial network as cells lacking essential fusion genes Mfn1 and Mfn2 displayed increased heterogeneity in mitochondrial protein age. Experiments in hippocampal neurons illustrate that the distribution of older and younger mitochondrial protein within the cell is determined by subcellular spatial organization and compartmentalization of mitochondria into neurites and soma. This effect was altered by overexpression of mitochondrial transport protein, RHOT1/MIRO1. Collectively our data show that distribution of young and old protein in the mitochondrial network is dependent on turnover, fusion, and transport.
Collapse
Affiliation(s)
- Andrew W Ferree
- Department of Medicine, Obesity and Nutrition Section; The Mitochondria Affinity Research Collaborative; Evans Biomedical Research Center; Boston University School of Medicine; Boston, MA USA
| | - Kyle Trudeau
- Department of Medicine, Obesity and Nutrition Section; The Mitochondria Affinity Research Collaborative; Evans Biomedical Research Center; Boston University School of Medicine; Boston, MA USA
| | - Eden Zik
- Department of Medicine, Obesity and Nutrition Section; The Mitochondria Affinity Research Collaborative; Evans Biomedical Research Center; Boston University School of Medicine; Boston, MA USA
| | - Ilan Y Benador
- Department of Medicine, Obesity and Nutrition Section; The Mitochondria Affinity Research Collaborative; Evans Biomedical Research Center; Boston University School of Medicine; Boston, MA USA
| | - Gilad Twig
- Department of Medicine, Obesity and Nutrition Section; The Mitochondria Affinity Research Collaborative; Evans Biomedical Research Center; Boston University School of Medicine; Boston, MA USA
- Department of Medicine and the Dr. Pinchas Bornstein Talpiot Medical Leadership Program 2012; Sheba Medical Center; Tel-Hashomer, Israel
| | - Roberta A Gottlieb
- Department of Molecular Cardiobiology; Heart Institute; Cedars-Sinai Medical Center; Los Angeles, CA USA
| | - Orian S Shirihai
- Department of Medicine, Obesity and Nutrition Section; The Mitochondria Affinity Research Collaborative; Evans Biomedical Research Center; Boston University School of Medicine; Boston, MA USA
- Department of Clinical Biochemistry and Pharmacology; Faculty of Health Sciences; Ben-Gurion University of the Negev; Negev, Israel
| |
Collapse
|
37
|
Patergnani S, Marchi S, Rimessi A, Bonora M, Giorgi C, Mehta KD, Pinton P. PRKCB/protein kinase C, beta and the mitochondrial axis as key regulators of autophagy. Autophagy 2013; 9:1367-85. [PMID: 23778835 DOI: 10.4161/auto.25239] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Autophagy is the major intracellular system of degradation, and it plays an essential role in various biological events. Recent observations indicate that autophagy is modulated in response to the energy status of the mitochondrial compartment. However, the exact signaling mechanism that controls autophagy under these conditions remains unclear. In this study, we report that the activation of protein kinase C β (PRKCB), a member of the classical PRKCs, negatively modulates the mitochondrial energy status and inhibits autophagy. Furthermore, cells treated with a pharmacological PRKCB inhibitor, and prkcb knockout MEFs showed an increase in autophagy both in vitro and in vivo, as well as an increased mitochondrial membrane potential (Ψm), suggesting a strong involvement of mitochondrial energy in the modulation of the autophagy machinery. Finally, we show that factors that increase the Ψm oppose the PRKCB-dependent inhibition of autophagy. Altogether, these data underscore the importance of PRKCB in the regulation of autophagy; moreover, the finding that a pharmacological modulation of the Ψm modifies autophagy levels may be useful in fighting pathologies (including various types of cancer and neurodegenerative disorders) that are characterized by reduced levels of autophagy.
Collapse
Affiliation(s)
- Simone Patergnani
- Department of Morphology, Surgery and Experimental Medicine; Section of General Pathology; Interdisciplinary Center for the Study of Inflammation (ICSI); Laboratory for Technologies of Advanced Therapies (LTTA); University of Ferrara; Ferrara, Italy
| | | | | | | | | | | | | |
Collapse
|
38
|
Bayeva M, Khechaduri A, Wu R, Burke MA, Wasserstrom JA, Singh N, Liesa M, Shirihai OS, Langer NB, Paw BH, Ardehali H. ATP-binding cassette B10 regulates early steps of heme synthesis. Circ Res 2013; 113:279-87. [PMID: 23720443 DOI: 10.1161/circresaha.113.301552] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE Heme plays a critical role in gas exchange, mitochondrial energy production, and antioxidant defense in cardiovascular system. The mitochondrial transporter ATP-binding cassette (ABC) B10 has been suggested to export heme out of the mitochondria and is required for normal hemoglobinization of erythropoietic cells and protection against ischemia-reperfusion injury in the heart; however, its primary function has not been established. OBJECTIVE The aim of this study was to identify the function of ABCB10 in heme synthesis in cardiac cells. METHODS AND RESULTS Knockdown of ABCB10 in cardiac myoblasts significantly reduced heme levels and the activities of heme-containing proteins, whereas supplementation with δ-aminolevulinic acid reversed these defects. Overexpression of mitochondrial δ-aminolevulinic acid synthase 2, the rate-limiting enzyme upstream of δ-aminolevulinic acid export, failed to restore heme levels in cells with ABCB10 downregulation. ABCB10 and heme levels were increased by hypoxia, and reversal of ABCB10 upregulation caused oxidative stress and cell death. Furthermore, ABCB10 knockdown in neonatal rat cardiomyocytes resulted in a significant delay of calcium removal from the cytoplasm, suggesting a relaxation defect. Finally, ABCB10 expression and heme levels were altered in failing human hearts and mice with ischemic cardiomyopathy. CONCLUSIONS ABCB10 plays a critical role in heme synthesis pathway by facilitating δ-aminolevulinic acid production or export from the mitochondria. In contrast to previous reports, we show that ABCB10 is not a heme exporter and instead is required for the early mitochondrial steps of heme biosynthesis.
Collapse
Affiliation(s)
- Marina Bayeva
- Feinberg Cardiovascular Research Institute, Northwestern University School of Medicine, Chicago, IL
| | - Arineh Khechaduri
- Feinberg Cardiovascular Research Institute, Northwestern University School of Medicine, Chicago, IL
| | - Rongxue Wu
- Feinberg Cardiovascular Research Institute, Northwestern University School of Medicine, Chicago, IL
| | - Michael A Burke
- Feinberg Cardiovascular Research Institute, Northwestern University School of Medicine, Chicago, IL
| | - J Andrew Wasserstrom
- Feinberg Cardiovascular Research Institute, Northwestern University School of Medicine, Chicago, IL
| | - Neha Singh
- Feinberg Cardiovascular Research Institute, Northwestern University School of Medicine, Chicago, IL
| | - Marc Liesa
- Department of Medicine, Obesity and Nutrition Section, Mitochondria ARC, Evans Biomedical Research Center, Boston University School of Medicine, 650 Albany St., Boston, MA 02118, USA
| | - Orian S Shirihai
- Department of Medicine, Obesity and Nutrition Section, Mitochondria ARC, Evans Biomedical Research Center, Boston University School of Medicine, 650 Albany St., Boston, MA 02118, USA
| | - Nathaniel B Langer
- Hematology Division, Brigham & Women's Hospital; Hematology-Oncology Division, Children's Hospital Boston; Harvard Medical School, Boston, MA
| | - Barry H Paw
- Hematology Division, Brigham & Women's Hospital; Hematology-Oncology Division, Children's Hospital Boston; Harvard Medical School, Boston, MA
| | - Hossein Ardehali
- Feinberg Cardiovascular Research Institute, Northwestern University School of Medicine, Chicago, IL
| |
Collapse
|
39
|
Santo-Domingo J, Demaurex N. Perspectives on: SGP symposium on mitochondrial physiology and medicine: the renaissance of mitochondrial pH. ACTA ACUST UNITED AC 2013; 139:415-23. [PMID: 22641636 PMCID: PMC3362525 DOI: 10.1085/jgp.201110767] [Citation(s) in RCA: 146] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Jaime Santo-Domingo
- Department of Cell Physiology and Metabolism, University of Geneva, CH-1211 Geneva, Switzerland
| | | |
Collapse
|
40
|
The mitochondrial Na+/Ca2+ exchanger upregulates glucose dependent Ca2+ signalling linked to insulin secretion. PLoS One 2012; 7:e46649. [PMID: 23056385 PMCID: PMC3466326 DOI: 10.1371/journal.pone.0046649] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Accepted: 09/03/2012] [Indexed: 11/25/2022] Open
Abstract
Mitochondria mediate dual metabolic and Ca2+ shuttling activities. While the former is required for Ca2+ signalling linked to insulin secretion, the role of the latter in β cell function has not been well understood, primarily because the molecular identity of the mitochondrial Ca2+ transporters were elusive and the selectivity of their inhibitors was questionable. This study focuses on NCLX, the recently discovered mitochondrial Na+/Ca2+ exchanger that is linked to Ca2+ signalling in MIN6 and primary β cells. Suppression either of NCLX expression, using a siRNA construct (siNCLX) or of its activity, by a dominant negative construct (dnNCLX), enhanced mitochondrial Ca2+ influx and blocked efflux induced by glucose or by cell depolarization. In addition, NCLX regulated basal, but not glucose-dependent changes, in metabolic rate, mitochondrial membrane potential and mitochondrial resting Ca2+. Importantly, NCLX controlled the rate and amplitude of cytosolic Ca2+ changes induced by depolarization or high glucose, indicating that NCLX is a critical and rate limiting component in the cross talk between mitochondrial and plasma membrane Ca2+ signalling. Finally, knockdown of NCLX expression was followed by a delay in glucose-dependent insulin secretion. These findings suggest that the mitochondrial Na+/Ca2+ exchanger, NCLX, shapes glucose-dependent mitochondrial and cytosolic Ca2+ signals thereby regulating the temporal pattern of insulin secretion in β cells.
Collapse
|
41
|
Akhmedov D, De Marchi U, Wollheim CB, Wiederkehr A. Pyruvate dehydrogenase E1α phosphorylation is induced by glucose but does not control metabolism-secretion coupling in INS-1E clonal β-cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1823:1815-24. [PMID: 22809973 DOI: 10.1016/j.bbamcr.2012.07.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Revised: 06/25/2012] [Accepted: 07/09/2012] [Indexed: 12/24/2022]
Abstract
Glucose-induced insulin secretion from pancreatic β-cells depends on mitochondrial activation. In the organelle, glucose-derived pyruvate is metabolised along the oxidative and anaplerotic pathway to generate downstream signals leading to insulin granule exocytosis. Entry into the oxidative pathway is catalysed by pyruvate dehydrogenase (PDH) and controlled in part by phosphorylation of the PDH E1α subunit blocking enzyme activity. We find that glucose but not other nutrient secretagogues induce PDH E1α phosphorylation in INS-1E cells and rat islets. INS-1E cells and primary β-cells express pyruvate dehydrogenase kinase (PDK) 1, 2 and 3, which mediate the observed phosphorylation. In INS-1E cells, suppression of the two main isoforms, PDK1 and PDK3, almost completely prevented PDH E1α phosphorylation. Under basal glucose conditions, phosphorylation was barely detectable and therefore the enzyme almost fully active (90% of maximal). During glucose stimulation, PDH is only partially inhibited (to 78% of maximal). Preventing PDH phosphorylation in situ after suppression of PDK1, 2 and 3 neither enhanced pyruvate oxidation nor insulin secretion. In conclusion, although glucose stimulates E1α phosphorylation and therefore inhibits PDH activity, this control mechanism by itself does not alter metabolism-secretion coupling in INS-1E clonal β-cells.
Collapse
Affiliation(s)
- Dmitry Akhmedov
- Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland
| | | | | | | |
Collapse
|
42
|
Gaspers LD, Mémin E, Thomas AP. Calcium-dependent physiologic and pathologic stimulus-metabolic response coupling in hepatocytes. Cell Calcium 2012; 52:93-102. [PMID: 22564906 DOI: 10.1016/j.ceca.2012.04.009] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Revised: 04/13/2012] [Accepted: 04/16/2012] [Indexed: 01/19/2023]
Abstract
A recurrent paradigm in calcium signaling is the coordination of the target response of the calcium signal with activation of metabolic energy production to support that response. This occurs in many tissues, including cardiac and skeletal muscle where contractile activity and ATP production are coordinately regulated by the frequency and amplitude of calcium transients, endocrine and exocrine cells that use calcium to drive the secretory process, and hepatocytes where the downstream targets of calcium include both catabolic and anabolic processes. The primary mechanism by which calcium enhances the capacity for energy production is through calcium-dependent stimulation of mitochondrial oxidative metabolism, achieved by increasing NADH production and respiratory chain flux. Although this enhances energy supply, it also has the potential for deleterious consequences resulting from increased generation of reactive oxygen species (ROS). The negative consequences of calcium-dependent mitochondrial activation can be ameliorated when the underlying cytosolic calcium signals occur as brief calcium spikes or oscillations, with signal strength encoded through the spike frequency (frequency modulation). Frequency modulation increases signal fidelity, and reduces pathological effects of calcium, including excess mitochondrial ROS production and apoptotic or necrotic outcomes. The present article reviews these issues using data obtained in hepatocytes under physiologic and pathologic conditions.
Collapse
Affiliation(s)
- Lawrence D Gaspers
- Department of Pharmacology and Physiology, University of Medicine and Dentistry of New Jersey, 185 South Orange Avenue, Newark, NJ 07103, United States.
| | | | | |
Collapse
|
43
|
Wiederkehr A, Wollheim CB. Mitochondrial signals drive insulin secretion in the pancreatic β-cell. Mol Cell Endocrinol 2012; 353:128-37. [PMID: 21784130 DOI: 10.1016/j.mce.2011.07.016] [Citation(s) in RCA: 110] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Accepted: 07/07/2011] [Indexed: 12/31/2022]
Abstract
β-Cell nutrient sensing depends on mitochondrial function. Oxidation of nutrient-derived metabolites in the mitochondria leads to plasma membrane depolarization, Ca(2+) influx and insulin granule exocytosis. Subsequent mitochondrial Ca(2+) uptake further accelerates metabolism and oxidative phosphorylation. Nutrient activation also increases the mitochondrial matrix pH. This alkalinization is required to maintain elevated insulin secretion during prolonged nutrient stimulation. Together the mitochondrial Ca(2+) rise and matrix alkalinization assure optimal ATP synthesis necessary for efficient activation of the triggering pathway of insulin secretion. The sustained, amplifying pathway of insulin release also depends on mitochondrial Ca(2+) signals, which likely influence the generation of glucose-derived metabolites serving as coupling factors. Therefore, mitochondria are both recipients and generators of signals essential for metabolism-secretion coupling. Activation of these signaling pathways would be an attractive target for the improvement of β-cell function and the treatment of type 2 diabetes.
Collapse
|
44
|
Poburko D, Demaurex N. Regulation of the mitochondrial proton gradient by cytosolic Ca²⁺ signals. Pflugers Arch 2012; 464:19-26. [PMID: 22526460 DOI: 10.1007/s00424-012-1106-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Accepted: 04/02/2012] [Indexed: 12/16/2022]
Abstract
Mitochondria convert the energy stored in carbohydrate and fat into ATP molecules that power enzymatic reactions within cells, and this process influences cellular calcium signals in several ways. By providing ATP to calcium pumps at the plasma and intracellular membranes, mitochondria power the calcium gradients that drive the release of Ca²⁺ from stores and the entry of Ca²⁺ across plasma membrane channels. By taking up and subsequently releasing calcium ions, mitochondria determine the spatiotemporal profile of cellular Ca²⁺ signals and the activity of Ca²⁺-regulated proteins, including Ca²⁺ entry channels that are themselves part of the Ca²⁺ circuitry. Ca²⁺ elevations in the mitochondrial matrix, in turn, activate Ca²⁺-dependent enzymes that boost the respiratory chain, increasing the ability of mitochondria to buffer calcium ions. Mitochondria are able to encode and decode Ca²⁺ signals because the respiratory chain generates an electrochemical gradient for protons across the inner mitochondrial membrane. This proton motive force (Δp) drives the activity of the ATP synthase and has both an electrical component, the mitochondrial membrane potential (ΔΨ(m)), and a chemical component, the mitochondrial proton gradient (ΔpH(m)). ΔΨ(m) contributes about 190 mV to Δp and drives the entry of Ca²⁺ across a recently identified Ca²⁺-selective channel known as the mitochondrial Ca²⁺ uniporter. ΔpH(m) contributes ~30 mV to Δp and is usually ignored or considered a minor component of mitochondria respiratory state. However, the mitochondrial proton gradient is an essential component of the chemiosmotic theory formulated by Peter Mitchell in 1961 as ΔpH(m) sustains the entry of substrates and metabolites required for the activity of the respiratory chain and drives the activity of electroneutral ion exchangers that allow mitochondria to maintain their osmolarity and volume. In this review, we summarize the mechanisms that regulate the mitochondrial proton gradient and discuss how thermodynamic concepts derived from measurements in purified mitochondria can be reconciled with our recent findings that mitochondria have high proton permeability in situ and that ΔpH(m) decreases during mitochondrial Ca²⁺ elevations.
Collapse
Affiliation(s)
- Damon Poburko
- Department of Biomedical Physiology & Kinesiology, Simon Fraser University, Vancouver, BC, Canada
| | | |
Collapse
|
45
|
Ogata M, Awaji T, Iwasaki N, Fujimaki R, Takizawa M, Maruyama K, Iwamoto Y, Uchigata Y. A new mitochondrial pH biosensor for quantitative assessment of pancreatic β-cell function. Biochem Biophys Res Commun 2012; 421:20-6. [DOI: 10.1016/j.bbrc.2012.03.093] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Accepted: 03/16/2012] [Indexed: 10/28/2022]
|
46
|
Abstract
Mutations in cancer cells affecting subunits of the respiratory chain (RC) indicate a central role of oxidative phosphorylation for tumourigenesis. Recent studies have suggested that such mutations of RC complexes impact apoptosis induction. We review here the evidence for this hypothesis, which in particular emerged from work on how complex I and II mediate signals for apoptosis. Both protein aggregates are specifically inhibited for apoptosis induction through different means by exploiting with protease activation and pH change, two widespread but independent features of dying cells. Nevertheless, both converge on forming reactive oxygen species for the demise of the cell. Investigations into these mitochondrial processes will remain a rewarding area for unravelling the causes of tumourigenesis and for discovering interference options.
Collapse
|
47
|
Wiederkehr A, Szanda G, Akhmedov D, Mataki C, Heizmann CW, Schoonjans K, Pozzan T, Spät A, Wollheim CB. Mitochondrial matrix calcium is an activating signal for hormone secretion. Cell Metab 2011; 13:601-11. [PMID: 21531342 DOI: 10.1016/j.cmet.2011.03.015] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Revised: 12/30/2010] [Accepted: 03/11/2011] [Indexed: 12/18/2022]
Abstract
Mitochondrial Ca(2+) signals have been proposed to accelerate oxidative metabolism and ATP production to match Ca(2+)-activated energy-consuming processes. Efforts to understand the signaling role of mitochondrial Ca(2+) have been hampered by the inability to manipulate matrix Ca(2+) without directly altering cytosolic Ca(2+). We were able to selectively buffer mitochondrial Ca(2+) rises by targeting the Ca(2+)-binding protein S100G to the matrix. We find that matrix Ca(2+) controls signal-dependent NAD(P)H formation, respiration, and ATP changes in intact cells. Furthermore, we demonstrate that matrix Ca(2+) increases are necessary for the amplification of sustained glucose-dependent insulin secretion in β cells. Through the regulation of NAD(P)H in adrenal glomerulosa cells, matrix Ca(2+) also acts as a positive signal in reductive biosynthesis, which stimulates aldosterone secretion. Our dissection of cytosolic and mitochondrial Ca(2+) signals reveals the physiological importance of matrix Ca(2+) in energy metabolism required for signal-dependent hormone secretion.
Collapse
Affiliation(s)
- Andreas Wiederkehr
- Department of Cell Physiology and Metabolism, University of Geneva, University Medical Center, Switzerland.
| | | | | | | | | | | | | | | | | |
Collapse
|